Inkjet printers that record images by ejecting fine droplets of ink toward a base material from a plurality of outlets of a head while moving the base material relative to the head are conventionally used. Japanese Patent Application Laid-Open No. 2006-88342 discloses a technique in which, even if the landing position of ink ejected from a certain nozzle is shifted in the direction of arrangement of nozzles (the direction orthogonal to the feed direction of recording paper) due to a processing error in the nozzle or the like, the shift in the landing position is corrected by supplying one of five types of driving signals, each indicating different ejection timing, to an actuator while moving the inkjet head in the direction parallel to the direction of arrangement of nozzles, and thereby causing the nozzle whose ink landing position is shifted to have different ink ejection timing from other nozzles.
Furthermore, inkjet printers that include a first outlet row and a second outlet row arranged in a predetermined movement direction have also come into practical use, in which each outlet row has a plurality of outlets arranged with a fixed outlet pitch in a width direction perpendicular to the movement direction, and each outlet in the second outlet row is disposed halfway between each pair of adjacent outlets in the first outlet row with respect to the width direction. With such inkjet printers, although the outlets in each outlet row are spaced relatively far apart from one another, adjusting the ejection timing of the second outlet row with respect to that of the first outlet row allows the first outlet row and the second outlet row to form, with a fine pitch (i.e., at a high recording resolution), a plurality of dots arranged in a row in the width direction at each position in the movement direction.
Incidentally, in the inkjet printers including the first outlet row and the second outlet row, the ejection timing of the second outlet row with respect to that of the first outlet row is ideally determined based on the space in the movement direction between the first outlet row and the second outlet row and the relative movement speed of the head and the base material. However, in actuality, the characteristics of ink ejection (e.g., the direction and speed of ink ejection) vary depending on each outlet row, and thus the ejection timing of the second outlet row with respect to that of the first outlet row needs to be adjusted individually. If the ejection timing is not appropriately adjusted, dots formed with the first outlet row and dots formed with the second outlet row are spaced apart from one another in the movement direction, as a result of which the quality of images to be recorded is degraded. The ejection timing can be corrected by, for example, recording a predetermined test pattern on a base material and observing the test pattern under a loupe or a microscope, but this requires complex operations and a long time to correct the ejection timing.